Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
  • C23G5/02—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents
  • C23G5/028—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents containing halogenated hydrocarbons
  • C23G5/02803—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents containing halogenated hydrocarbons containing fluorine
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/50—Solvents
  • C11D7/5036—Azeotropic mixtures containing halogenated solvents
  • C11D7/504—Azeotropic mixtures containing halogenated solvents all solvents being halogenated hydrocarbons
  • C11D7/505—Mixtures of (hydro)fluorocarbons
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/26—Cleaning or polishing of the conductive pattern

Definitions

• This invention relates to azeotrope-like compositions of 1,1,1-trifluorohexane and perfluoromethylcyclohexane which are useful in a variety of industrial cleaning applications including defluxing of printed circuit boards.
• Fluorocarbon based solvents have been used extensively for the degreasing and otherwise cleaning of solid surfaces, especially intricate parts and difficult to remove soils.
• vapor degreasing or solvent cleaning consists of exposing a room temperature object to be cleaned to the vapors of a boiling solvent. Vapors condensing on the object provide clean distilled solvent to wash away grease or other contamination. Final evaporation of solvent leaves the object free of residue. This is contrasted with liquid solvents which leave deposits on the object after rinsing.
• a vapor degreaser is used for difficult to remove soils where elevated temperature is necessary to improve the cleaning action of the solvent, or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently.
• the conventional operation of a vapor degreaser consists of immersing the part to be cleaned in a sump of boiling solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room temperature, and finally exposing the part to solvent vapors over the boiling sump which condense on the cleaned part
• the part can also be sprayed with distilled solvent before final rinsing.
• Vapor degreasers suitable in the above-described operations are well known in the art.
• Sherliker et al. in U.S. Pat. No. 3,085,918 disclose a suitable vapor degreaser comprising a boiling sump, a clean sump, a water separator, and other ancillary equipment.
• Cold cleaning is another application where a number of solvents are used. In most cold cleaning applications, the soiled part is either immersed in the fluid or wiped with cloths soaked in solvents and allowed to air dry.
• azeotropic compositions preferably those which include halocarbon components like trichlorotrifluoroethane and other components which contribute additionally desired characteristics, such as polar functionality, increased solvency power, and stabilizers.
• Azeotropic compositions are desired because they do not fractionate upon boiling. This behavior is desirable because in the previously described vapor degreasing equipment with which these solvents are employed, redistilled material is generated for final rinse cleaning. Thus, the vapor degreasing system acts as a still. Therefore, unless the solvent composition is essentially constant boiling, (i.e., is an azeotrope or azeotrope-like) fractionation will occur and undesirable solvent distribution may act to upset the cleaning and safety of processing.
• preferential evaporation of the more volatile components of the solvent mixtures would result in mixtures with changed compositions which may have less desirable properties, like lower solvency towards soils, less inertness towards metal, plastic or elastomer components, and increased flammability and toxicity.
• fluorocarbon based azeotrope-like mixtures are of particular interest because they are considered to be stratospherically safe substitutes for presently used fully halogenated chlorofluorocarbons (like trichlorotrifluoroethane). The latter have been implicated in causing environmental problems associated with the depletion of the earth's protective ozone layer.
• the invention relates to azeotrope-like compositions of 1,1,1-trifluorohexane and perfluoromethylcyclohexane which are useful in a variety of industrial cleaning applications including defluxing of printed circuit boards.
• novel azeotrope-like compositions comprising 1,1,1-trifluorohexane and perfluoromethylcyclohexane.
• the azeotrope-like compositions comprise from about 18 to about 61 weight percent 1,1,1-trifluorohexane and from about 39 to about 82 weight percent perfluoromethylcyclohexane and boil at about 66.4.C. ⁇ 0.5° C. at 746 mm Hg.
• the azeotrope-like compositions of the invention comprise from about 18 to about 49 weight percent 1,1,1-trifluorohexane and from about 51 to about 82 weight percent perfluoromethylcyclohexane.
• the azeotrope-like compositions of the invention comprise from about 18 to about 25 weight percent 1,1,1-trifluorohexane and from about 75 to about 82 weight percent perfluoromethylcyclohexane.
• the 1,1,1-trifluorohexane component of the invention has good solvent properties, but is flammable.
• the perfluoromethylcyclohexane component has poorer solvent properties but is nonflammable.
• a synergistic blend having azeotropic properties results which is nonflammable and has good solvent capabilities.
• additives like alcohols may be added to the solvent composition of the invention to change the polarity of the solvent blend enabling the solvent to dissolve more polar contaminants or soils.
• Suitable alcohols include methanol, ethanol, isopropanol, butanol and mixtures thereof.
• the perfluoromethylcyclohexane (C 7 F 14 , m.p. -37° C., b.p. 76° C.) component of the invention is commercially available. It may be purchased, for example, from PCR, Inc. of Gainsville, Fl. Alternately, it may be prepared via cobalt trifluoride fluorination of benzotrifluoride. See, W. B. Burford, III, et al., Ind. Eng. Chem., 1947, 39, 319.
• the 1,1,1-trifluorohexane component of the invention may be prepared in accordance with the synthesis set forth in Example 1 below. Other methods of preparing perfluoromethylcyclohexane and 1,1,1-trifluorohexane will readily occur to those skilled in the art.
• the perfluoromethylcyclohexane and 1,1,1-trifluorohexane components of the invention should be used in sufficiently high purity so as to avoid the introduction of adverse influences upon the constant boiling properties of the system.
• compositions within the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like, as defined more particularly below.
• thermodynamic state of a fluid is defined by four variables: pressure, temperature, liquid composition and vapor composition, or P-T-X-Y, respectively.
• An azeotrope is a unique characteristic of a system of two or more components where X and Y are equal at the stated P and T. In practice, this means that the components of a mixture cannot be separated during distillation, and therefore are useful in vapor phase solvent cleaning as described above.
• azeotrope-like composition is intended to mean that the composition behaves like a true azeotrope in terms of its constant-boiling characteristics or tendency not to fractionate upon boiling or evaporation. Such composition may or may not be a true azeotrope.
• the composition of the vapor formed during boiling or evaporation is identical or substantially identical to the original liquid composition.
• the liquid composition if it changes at all, changes only slightly. This is contrasted with non-azeotrope-like compositions in which the liquid composition changes substantially during boiling or evaporation.
• one way to determine whether a candidate mixture is "azeotrope-like" within the meaning of this invention is to distill a sample thereof under conditions (i.e. resolution-- number of plates) which would be expected to separate the mixture into its components. If the mixture is non-azeotropic or non-azeotrope-like, the mixture will fractionate, (i.e. separate into its various components) with the lowest boiling component distilling off first, etc. If the mixture is azeotrope-like, some finite amount of a first distillation cut will be obtained which contains all of the mixture components and which is constant boiling or behaves as a single substance. This phenomenon cannot occur if the mixture is not azeotrope-like (i.e., it is not part of an azeotropic system).
• azeotrope-like compositions there is a range of compositions containing the same components in varying proportions which are azeotrope-like. All such compositions are intended to be covered by the term azeotrope-like as used herein.
• azeotrope-like As an example, it is well known that at different pressures, the composition of a given azeotrope will vary at least slightly as does the boiling point of the composition.
• an azeotrope of A and B represents a unique type of relationship but with a variable composition depending on temperature and/or pressure.
• another way of defining azeotrope-like within the meaning of this invention is to state that such mixtures boil within about ⁇ 2° C. (at 746 mm Hg) of the 65.9° C. boiling point disclosed herein.
• the boiling point of the azeotrope will vary with the pressure.
• the azeotrope-like compositions of the invention may be used to clean solid surfaces by treating said surfaces with said compositions in any manner well known to the art such as by dipping or spraying or use of conventional degreasing apparatus.
• the azeotrope-like compositions are used to clean solid surfaces by spraying the surfaces with the compositions, preferably, the azeotrope-like compositions are sprayed onto the surfaces by using a propellant.
• the propellant is selected from the group consisting of nonflammable chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, carbon dioxide, nitrogen, nitrous oxide, air, and mixtures thereof.
• Useful chlorofluorocarbon propellants include trichlorofluoromethane (known in the art as CFC-11), dichlorodifluoromethane (known in the art as CFC-12), 1,1,2-trichloro-1,2,2-trifluoroethane (known in the art as CFC-113), and 1,2-dichloro-,1,1,2,2-tetrafluoroethane (known in the art as CFC-114); commercially available CFC-11, CFC-12, CFC-113, and CFC-114 may be used in the present invention.
• CFC-11 trichlorofluoromethane
• CFC-12 dichlorodifluoromethane
• CFC-113 1,1,2-trichloro-1,2,2-trifluoroethane
• CFC-114 1,2-dichloro-,1,1,2,2-tetrafluoroethane
• Useful hydrochlorofluorocarbon propellants include dichlorofluoromethane (known in the art as HCFC-21), chlorodifluoromethane (known in the art as HCFC-22), 1-chloro-1,2,2,2-tetrafluoroethane (known in the art as HCFC-124), 1,1-dichloro-2,2-difluoroethane (known in the art as HCFC-132a), 1-chloro-2,2,2-trifluoroethane (known in the art as HCFC-133), and 1-chloro-1-difluoroethane (known in the art as HCFC-42b); commercially available HCFC-21, HCFC-22 and HCFC-42b may be used in the present invention.
• HCFC-24 may be prepared by a known process such as that taught by U.S. Pat. No. 4,843,181
• HCFC-133 may be prepared by a known process such as that taught by U.S. Pat.
• Useful hydrofluorocarbon propellants include trifluoromethane (known in the art as HFC-23), 1,1,1,2-tetrafluoroethane (known in the art as HFC-34a), and 1,1-difluoroethane (known in the art as HFC-152a); commercially available HFC-23 and HFC-152a may be used in the present invention. Until HFC-134a becomes available in commercial quantities, HFC-134a may be prepared by any known method such as that disclosed by U.S. Pat. NO. 4,851,595. More preferred propellants include hydrochlorofluorocarbons and hydrofluorocarbons. The most preferred propellants include chlorodifluoromethane and 1,1,1,2-tetrafluoroethane.
• the compositional range over which 1,1,1-trifluorohexane and perfluoromethylcyclohexane exhibit constant boiling behavior was determined using ebulliometry.
• the ebulliometer consisted of a heated sump in which the perfluoromethylcyclohexane was brought to a boil. The upper part of the ebulliometer connected to the sump was cooled, thereby acting as a condenser for the boiling vapors, allowing the system to operate at total reflux. After bringing the perfluoromethylcyclohexane to a boil at atmospheric pressure, measured amounts of 1,1,1-trifluorohexane were titrated into the ebulliometer. The change in boiling point was measured using a mercury thermometer graduated from 50 to 80° C. in 0.1° C. increments.
• a 72.5/27.5 weight percent mixture of perfluoromethylcyclohexane and 1,1,1-trifluorohexane respectively was prepared. To this mixture was added 7 volume percent mineral oil. The solvent/mineral oil mixture was refluxed. The 1,1,1-trifluorohexane and perfluoromethylcyclohexane mixture readily dissolved the mineral oil at reflux as determined by visual inspection and consequently, would remove soils of this type under vapor degreasing conditions.
• the flash point of a 26.7/73.3 weight percent mixture of 1,1,1-trifluorohexane and perfluoromethylcyclohexane respectively was determined using the SETA flash closed-cup flashpoint tester.
• the 1,1,1-trifluorohexane and perfluoromethylcyclohexane mixture failed to exhibit a closed cup flashpoint up to an operating temperature of 150° F.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• General Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Detergent Compositions (AREA)

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Citations (12)

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• 1991
  • 1991-10-21 US US07/779,687 patent/US5182042A/en not_active Expired - Fee Related
• 1992
  • 1992-08-13 AU AU24962/92A patent/AU2496292A/en not_active Abandoned
  • 1992-08-13 WO PCT/US1992/006794 patent/WO1993008256A1/fr not_active Ceased

Patent Citations (12)

Non-Patent Citations (7)

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